Brake control means



March 24, 1942. J. CANETTA ET AL 2,277,035

BRAKE CONTROL MEANS Filed Aug. 31, 1940 2 Shets-Sheet 1 1L Y A I m; M Ns R EEO O VNB T NA T K E NL m OPY r E J B A m m mm MM, 8% R NY I w 000BMM D OBO o m. a 5 a m .QMW m mm NW 3 in Q Q Na M 3 t 3 3 3 Sq H h 1 H El1 7 l fi i NX wLr TJA: 8

March 24, 1942. J. CANETTA ETAL 2,277,035

BRAKE CONTROL MEANS Filed Aug. 51, 1940 2 Sheets-Sheet 2 v INVENTOR JOHNCANETTA 5 ml, NEOSBART ATTORNEY Patented Mar. 24, 1942 UNITED STATESPATENT OFFICE.

BRAKE CONTROL MEANS Application August 31, 1940, Serial No. 354,938

11 Claims.

This invention relates to brake control means for vehicles, such asrailway cars and trains, and has particular relation to brake controlapparatus including means for detecting the slipping of a vehicle wheelor wheel unit and causing the rapid.

release of the brakes associated with the slipping wheel or wheel unitto prevent the sliding thereof.

As is well known, if the brakes are applied on a vehicle wheel to asufficient degree to exceed the adhesion or rolling friction between therim of the Wheel and road surface or the rails on which the wheel rolls,the wheel decelerates at an abnormally rapid rate to a locked-wheelcondition and slides. The term slip or slipping condition as employedherein refers to the rotation of a vehicle wheel at a speed less than aspeed corresponding to vehicle speed at a given instant, whereas theterm slide or sliding condition refers to the dragging of a vehiclewheel along a road surface or rail in a locked condition. Thedistinction between the two terms should be borne in mind.

Various types of apparatus have been proposed for detecting the slippingcondition of a vehicle wheel. One such type of apparatus includes meansresponsive to the difference in the respective speeds of two separatelyrotatable vehicle wheels occurring when one of the wheels slips.

It is an object of our present invention to provide a novel arrangementfor detecting the differenoe in the respective speeds of rotation of tworotary elements and effective in connection with two separatelyrotatable vehicle wheels for detecting the slipping condition of one ofthe wheels.

It is another object of our invention to provide, in a brake controlequipment for vehicle wheels, a novel arrangement for detecting thereduction in speed of a slipping vehicle wheel or wheel unit withreference to another preferably underbraked wheel or wheel unit andcausing a rapid reduction of the brakes associated with the slippingwheel or wheel unit to prevent sliding thereof.

It is another object of our invention to provide a novel relay device ofthe induction motor type having a rotor subject to an actuating torqueforce varying according to the difference in frequency of alternatingcurrent supplied to two different sets of polyphase windings thereofrespectively.

It is another object of our invention to provide a novel arrangement fordetecting the difference in the respective speeds of two separatelyrotatable members, including a source of alternating current voltage foreach rotatable member varying in frequency according to the rotationalspeed of the respective members for energizing the corresponding sets ofpolyphase windings of a relay of the type indicated in the previousobject.

The above objects, and other objects of our invention which will be madeapparent hereinafter, are attained by means of several embodiments ofour invention subsequently to be described and shown in the accompanyingdrawings, wherein Fig. 1 is a simplified diagrammatic view, showing abrake control equipment for a single railway car, of the two truck type,having one embodiment of our invention applied thereto.

Fig. 2 is an enlarged plan view, partly in section, showing details ofthe commutator devices associated with the individual wheels or wheelunits shown in Fig. 1, and

Fig. 3 is an enlarged diagrammatic view, showing a modified type ofrelay which may be substituted for the type of relay device shown inFig. 1.

Description of embodiment shown in Fig. 1

Referring to Fig. 1, the brake control equipment shown therein is thatfor a single car having a four-wheel truck H at one end thereof and afour-wheel truck [2 at the opposite end thereof. Each truck has twoseparately rotatable wheel units comprising two wheels l3, only one ofwhich is shown in the drawings, connected by and fixed to a connectingaxle I4 in conventional manner.

The brakes associated with the wheels l3 may be of the usual clasp typein which the brake shoes are operated into and out of engagement withthe rim or tread of the wheels through brake rigging (not shown) inresponse to the supply of fluid under pressure to and the release offluid under pressure from brake cylinders 15. The term wheel unit asemployed herein may designate a single wheel or any number of wheelsmechanically connected, as by an axle, to rotate together. In Fig. 1 twobrake cylinders are shown for each wheel truck, one brake cylinder beingeffective to operate the brake associated with one wheel unit and theother brake cylinder being effective to operate the brakes associatedwith the other wheel unit of the same truck. Obviously, any desirednumber of brake cylinders may be employed.

The-brake cylinder l5 associated with one of the wheel units of thetruck II is of smaller diameter than the others so that the effectiveforce thereof for a given fluid pressure supplied to the brake cylindersis less than that of the other brake cylinders. The wheel unit withwhich this smaller brake cylinder is associated will hereinafter bereferred to as the underbraked wheel unit. The purpose of the smallerbrake cylinder for the one wheel unit is to so limit the degree ofapplication of the brakes associated with the wheel unit that at no timecan the wheels of this wheel unit slip but rotate at all times inaccordance with the speed of travel of the car. The manner in which thisfeature is utilized will be made apparent hereinafter.

Fluid under pressure may be supplied to the brake cylinders l5 andreleased therefrom, under the control of the operator of the vehicle, byany suitable apparatus. For simplicity, we have illustrated an apparatusof the straight-air type employing a train pipe, hereinafter referred toas the control pipe IT, to which the brake cylinders I5 are connected bybranch pipes l8, and a manually operated brake valve 19 of theself-lapping type for controlling the pressure in the control pipe I!and the connected brake cylinders l5. The pneumatic brake controlequipment further includes a source of fluid under pressure, such as areservoir 2| that is normally charged to a certain pressure such as onehundred pounds per square inch by means of a fluid compressor not shown,and a train pipe, hereinafter referred to as the supply pipe 22,connected to the reservoir 2! and charged to the pressure therein.

The control pipe I! and supply pipe 22 extend, in conventional manner,from one end of a car to the other and are provided at the ends thereofwith suitable angle cocks 23 and hose couplings 24 for connecting thesections of the pipes on successive cars in the usual manner.

The brake valve I9 is connected to the pipes H and 22 by branch pipes 25and 26 respectively, in each of which a manually operated valve 21 isinterposed. The valves 21 are in open position when it is'desired tohave the brake valve .l9 control the pressure in the control pipe 91.When it is desired to control the pressure in the pipe I! by means of abrake valve corresponding to the brake valve IS on another car, thevalves 21 are closed, thus cutting the brake valve 19 of Fig. 1 out ofoperation.

The brake valve I9 is of well-known construction and accordingly afunctional description thereof is deemed suflicient for the purposes ofthe present application. The brake valve I9 has an operating handle 19awhich is effective when shifted in a horizontal plane to rotate a rotaryoperating shaft that in turn causes operation of the valve mechanism ofthe brake valve. When the brake valve handle life is in its normal orbrake release position, the valve mechanism of the brake valve isconditioned to cause the release of fluid under pressure from thecontrol pipe I! through an exhaust port and pipe 28 at the brake valve.When the brake valve handle l9a is shifted in a horizontal plane out ofits normal position into a so-called application zone,

the valve mechanism of the brake valve is oper- Y ated to cause fluidunder pressure to be supplied from the supply pipe 22 and connectedreservoir 2| to the control pipe I! to establish a pressure thereinwhich corresponds substantially to the degree of displacement of thebrake valve handle out of its normal position.

If the pressure in the control pipe I! tends to reduce for some reason,such a leakage, the valve mechanism of the brake valve is automaticallyoperative to maintain a supply of fluid under pressure to the controlpipe so that a pressure corresponding to the position of the brake valvehandle is maintained in the control pipe IT. This pressure-maintainingfeature of the brake valve [9 will be referred to hereinafter.

According to our invention, the equipment shown in Fig. 1 furthercomprises a magnet valve device 3| interposed in the branch pipe I8leading to the brake cylinders of each wheel truck, and a relay device32 for each of the wheel units of the vehicle except the underbrakedwheel unit, adapted to control the magnet valve device 31 of thecorresponding wheel truck.

The equipment further includes a source of two-phase alternating-currentadapted to have a frequency, hereinafter referred to as the masterfrequency, proportional to the rotational speed of the underbraked wheelunit of wheel truck I l and, associated with each of the other wheelunits of the vehicle an individual source of two-phasealternating-current adapted to have a frequency corresponding to therotational speed of the corresponding wheel unit and hereinafterreferred to as the local frequency. The various sources of two-phasealternating-current may be of any desired and suitable construction. Asshown, these sources respectively comprise a commutator or rotary switchdevice 33 driven according to the rotational speed of the correspondingwheel unit, as by direct connection to the end of the corresponding axleI4 in the manner presently to be described, and a pair of voltage-translating devices or transformers 34 and 35.

The relay devices 32 are so constructed and arranged, as hereinafter tobe explained, as to operatively respond to a predetermined difierence inthe master frequency and the corresponding local frequency which occurswhenever the corresponding wheel unit slips.

Referring in greater detail to the parts of the equipment, the magnetvalves 3| for th two wheel trucks are identical and accordingly onlythat for the wheel truck H is shown in detail. Each magnet valve 3|comprises a pair of oppositely seating valves 43 and 44 of the poppettype which are normally biased upwardly by a coil spring 45 to unseatedand seated positions respectively. With the valves 43 and 44 sopositioned, communication is established through the branch pipe 18 fromthe control pipe I? to the brake cylinders l5. Each magnet valve furthercomprises an electromagnet winding 46 which is effective, whenenergized, to actuate a plunger 47 to shift the valves 43 and 44downwardly to seated and unseated positions respectively. With thevalves so positioned, the communication through the branch pipe 18 fromthe control pipe to the brake cylinders is closed and an exhaustcommunication is established through which fluid under pressure isreleased to atmosphere from the brake cylinders through an exhaust port48 at a rapid rate. Upon deenergization of the magnet winding 46, thespring 45 restores the valves to the unseated and seated positionsthereof, thereby closing the exhaust communication and reestablishingthe supply communication to the brake cylinders.

As diagrammatically shown, each relay device 32 comprises a statorelement or frame 5| and a rotor 52. Although not shown in detail, itshould be understood that the stator element 5| is similar to the statorof an induction motor and includes a laminated magnetic core structuresuitably slotted for receiving the stator windings in the conventionalmanner. The rotor 52 is similar to a conventional squirrel-cage rotor ofan induction motor and is suitably mounted on a shaft 53 journaled inthe stator frame in manner not shown. The outside diameter of the rotor52 is such as to provide a suitable air gap between itself and themagnetic core of the stator element 51.

Mounted in conventional manner in the usual slots of the stator core ortwo sets of polyphase windings, shown as two-phase windings,diagrammatically indicated for simplicity as phases A and B with eitherof the suflix numbers 1 and 2 depending upon the particular set ofwindings. The two-phase windings Al and BI may be associated with thetwo-phase windings A2 and B2 in any suitable manner as by having theconductors of corresponding phase windings received in the same slots atdifferent depths. It will be understood that the stator phase-windingsmay be distributed in the usual manner of induction or synchronous motorstator windings to provide any desired number of magnetic poles such as2, 4, 8, etc., within the physical limitation of the device.

Attached to one end of the rotor 52 is a contact arm 54, at least aportion of which is of insulating material. A coil spring 56, secured atone end to the contact arm 54 and at the other end to a lug 51 attachedto the stator frame,

biases the contact arm in a direction to normal 1y engage a fixed stop55 on the stator frame 5|. A contact 58 fixed on the contact arm 54 iselfective to bridge or connect two stationary contacts 59 and 66,carried in insulated relation on the frame 5! as by an insulating member6|, when the arm 54 is shifted in a clockwise direction out of itsnormal position in response to the rotary movement of the rotor 52,

The phase windings Al and BI of each of the relays 32 are connected tothree train Wires 31, 38 and 39 over which the two-phasealternatingcurrent or master frequency is supplied in a manner presentlyto be described. The energization of the windings Al and BI by atwo-phase current is effective, in manner well understood by thoseskilled in the art of induction motors, to produce a magnetic fieldwhich rotates in one direction at a speed corresponding to the frequencyof the supply.

The phase windings A2 and B2 are so connected and arranged as to beenergized by the local frequency or two-phase alternating-currentsupplied from the corresponding wheel unit source. The arrangement ofthe phase windings A2 and B2 is such that upon energization, themagnetic field produced thereby rotates in the opposite direction tothat of the magnetic field produced by the phase windings AI and BI andat a speed corresponding to the local frequency.

As long as the master frequency supplied to the windings Al and BI andthe local frequency supplied to the windings A2 and B2 are the same orsubstantially so, the respective torques exerted on the rotor 52 inresponse to each of the oppositely rotating magnetic fields produced bythe two sets of windings are substantially equal or balanced so that thecontact arm 54 remains biased by the spring 56 to the position, asshown, engaging the stop 55 and separating contact 53 from itsassociated pair of contacts 59 and 60.

When the local frequency supplied to the windings A2 and B2 becomes lessthan the master frequency supplied to the windings AI and BI of aparticular relay 32, an unbalanced torque is exerted on the rotorvarying in degree according to the difference between the masterfrequency and local frequency. When a sufiicient difference between themaster frequency and the local frequency occurs, the unbalanced torqueexerted on the rotor 52 is sufiicient to overcome the biasing force ofthe spring 56 and the rotor is accordingly shifted rotarily in aclockwise direction to effect engagement of the contact 58 on thecontact arm 54 with the associated pair of stationary contacts 59 and66.

It is desirable to construct the squirrel-cage I rotor 52 of relativelyhigh resistance metal, for reasons well known to those skilled in theart of induction motors, in order that an adequate- 1y high torque beexerted on the rotor 52 in response to a small difference between themaster and local frequencies so as to cause engagement of the contact 58on the contact arm with its associated pair of contacts 59 and 66.

It will be understood that since the underbraked wheel unit of the wheeltruck ll rotates at all times at a speed in accordance with the speed oftravel of the car, the master frequency corresponds at all times to thespeed of travel of the vehicle. The reduction in the local frequency ofthe two-phase alternating-current supplied to the phase windings A2 andB2 of each relay 32 accordingly reflects the reduction in speed of theindividual wheel unit relative to that of the underbraked wheel unitwhen the individual wheel unit slips. It will accordingly be seen thatwhenever any of the wheel units other than the underbraked wheel unitbegins to slip, the contacts 58 of the contact arm 54 of thecorresponding relay 32 is automatically and promptly actuated intoengagement with its associated pair of stationary contacts 59 and 66.

The switch formed by the contacts 58, 59 and 60 of each relay 32 servesto control a circuit for energizing and deenergizing the magnet winding46 of the magnet valve 3| for the corresponding wheel truck. To thisend, the contact 66 of each relay 32 is connected to a wire 62 to whichone terminal, such as the positive terminal, of a source ofdirect-current indicated as a storage battery 63 is connected. Thecontact 59 of the relay 32 associated with the one wheel unit of thewheel truck H is connected by a wire 65 to one terminal of the magnetwinding 46 of the magnet valve 3| for the wheel truck II, the opposite.terminal of the magnet winding 46 being connected to the oppositeterminal of the battery 63 as through a ground connection in the mannershown. The contact 59 of the two relays 32 for the wheel truck l2 areconnected to a wire 66 which is connected to one terminal of the magnetwinding 46 of the magnet valve 3| for the wheel truck l2, the oppositeterminal of the magnet Winding of this magnet valve being connected tothe opposite terminal of the battery 63 as through a ground connectionin the manner shown.

The manner in which a commutator device 33 and its associated pair oftransformers 34 and 35 cooperate to supply a two-phasealternatingcurrent having a frequency corresponding to the rotationalspeed of the corresponding wheel unit will now be briefly described.

As seen in Fig. 2, each commutator device 33 comprises a cylindricalelement H of suitable insulating material, such as hard rubber orBakelite having a flange at one end which is secured to one end of awheel axle l4 as by a plurality of screws 13 in such a manner that theelement H is coaxial to the axle l4 and rotates in correspondencetherewith. Embedded in the element 1| during the moulding operation, orotherwise suitably affixed thereto, is a contact ring 14 having acontinuous portion 15 extending circumferentially around the peripheryof the element 1| and an interrupted portion comprising a plurality ofspaced contact fingers '16. The contact ring 14 is preferably integrallyformed of suitable material such as copper, brass or alloys thereof.

As will be seen in Fig. 1, there are eight contact fingers 16 of uniformwidth and spacing separated by portions of the insulating element 1|intervening therebetween and resembling somewhat the commutator of aconventional direct-current electric motor. It will be understood thatanydesired number of contact fingers 16 may be provided, eight beingshown merely for purposes of illustration.

Arranged in a suitable brush holder, not shown, are three brushes (9, 88and 8|, the brush holder being in turn suitably supported within thejournal casing (not shown) at the end of each wheel axle. Brush '19 isso arranged and mounted as to constantly engage only the continuousportion 15 of the contact ring 14, whereas the brushes 80 and 8| arearranged in displaced relation thereto so as to engage only the contactfingers 76 of the contact ring 14.

The brushes 80 and 8| may occupy any angular position relative to eachother as long as they are displaced the equivalent of ninety electricaldegrees apart. As will be explained more fully presently, each contactfinger 15 is of a width corresponding to one hundred and eightyelectrical degrees and each intervening portion of the insulatingelement H between successive contact fingers 15 is likewise of a widthcorresponding to one hundred and eighty electrical degrees.

The brush 1!) of each commutator device 33 is connected by a branch wire85 to a bus or train wire 86 which is constantly connected by a branchwire 81 to one terminal, for example the positive terminal, of asuitable source of direct-current voltage, such as storage battery 88.

The brush 80 is connected by a wire 89 to one terminal of the primarywinding 34p of the associated transformer 34, the other terminal of theprimary winding of the transformer being connected to a bus wire 9| thatis constantly connected to the negative terminal of the battery 88.

In a similar manner, the brush BI is connected by a wire 92 to oneterminal of the primary winding 35p of the associated transformer 35,the other terminal of the primary winding of the transformer beingconnected to the bus wire 9|.

A suitable condenser 93 is connected between the brush l9 and the brush80, and a similar condenser 93 is connected between the brush l9 and thebrush Bl, for the purpose of reducing arcing at the brushes 80 and 8!when the brushes disengage the contact fingers '16.

It will thus be seen that as a commutator device 33 rotates, the primarywindings 34p and 35p of the corresponding pair of transformers aresuccessively energized and deenergized at a frequency depending upon thespeed of rotation of the commutator device, which is in turnproportional to the speed of rotation of the associated wheel unit. Itwill also be seen that due to the fact that the brushes 89 and BI arearranged in a manner to be separated ninety electrical degrees, thesuccessive cycles of energization and deenergization of the primarywindings 34p and 35p of each pair of transformers 34 and 35 arerespectively displaced ninety electrical degrees and that consequentlythe alternating-current voltage cycles induced in the correspondingsecondary windings 34s and 35s of the transformers are likewisedisplaced ninety electrical degrees in the manner characteristic oftwo-phase alternating-current.

In the case of the underbraked wheel unit of the wheel truck H, thesecondary windings 34s and 35s are so connected to the train wires 31,38 and 39 as to provide the two-phase alternating-current or masterfrequency supply to the phase windings Al and BI of all the relays 32.

A speedometer 95, in the form of a frequency meter, is connected acrossthe wires 31 and 38 to record the frequency in one of the phases. Forconvenience, the scale of the speedometer is calibrated in miles perhour. Since the underbraked wheel unit of truck ll always rotates at aspeed corresponding to vehicle speed, it will be apparent that thespeedometer 95 indicates the speed of the vehicle. Speedometer 95 may belocated in a convenient location adjacent the brake valve I9 in thecontrol cab of the vehicle so as to be visible by the operator at alltimes.

In the case of each of the wheel units other than the underbraked wheelunit, the secondary windings 34s and 35s of the corresponding pair oftransformers are so arranged and connected as to supply a two-phasealternating-current, having a frequency corresponding to the speed ofrotation of the wheel unit and referred to hereinbefore as the localfrequency, to the phase windings A2 and B2 of the corresponding relays32.

The ratio of the number of turns in the primary and secondary windingsof the transformers 34 and 35 is uniform so that the voltage across anyone phase of either the master frequency source or the local frequencysource is substantially the same,

In view of the fact that the source of master frequency associated withthe underbraked wheel unit supplies power to the phase windings AI andBI of all of the relays 32 whereas the sources of local frequency arerequired to supply power only to the one set of phase windings A2 and B2of the corresponding relay, it may be desirable to provide a two-phasealternating-current generator driven according to the speed of rotationof the underbraked wheel unit so as to obtain adequate power to properlyenergize the phase windings Al and BI of all of the relays on thevehicle. It is necessary, however, that the voltage characteristic ofthe generator simulate closely the voltage characteristic of the sourcesof local frequency.

If it is desired to have the vehicle travel in either a forward or areverse diretcion, it is necessary to provide suitable reversing switchmeans (not shown) preferably automatically responsive to a change indirection of rotation of the wheel axles or of the wheels themselves, toreverse the connections to one of the phase windings of each set on therelays 32, such as the connections to phase windings Al and A2.

The necessity for reversing the connections to one of the phase windingsof each group upon reversal of the direction of rotation of the vehiclewheels will be apparent from the fact that the phase rotation of thepolyphase voltages supplied to the respective sets of windings of therelays 32 reverses with a reversal of direction of rotation of thewheels l3, which in turn results in a reversal of the direction ofapplication of the torques respectively exerted by the two sets ofwindings of the relays on the rotor 52 thereof. In order to cause therotor 52 to move in the right direction to effect engagement of thecontact 58 with the stationary contacts 59 and 60 when wheel slipoccurs, the respective torques exerted by the two sets of windings ofthe relays must not change their direction of application with reversalof wheel rotation. Accordingly, by changing the connection of one phasewinding of each set upon reversal of wheel rotation, the phase rotationand the direction of application of the torques exerted by therespective sets of windings is maintained unchanged and consequently therotor 52 will always be shifted in the proper direction when wheel slipoccurs.

Operation of equipment shown in Fig. 1

Let it be assumed that a single car having the equipment shown in Fig. 1is traveling along the road under power with the brake valve handle |9ain its brake release position and that the operator desires to effect anapplication of the brakes. To do so, the operator first shuts offpropulsion power and then operates the brake valve handle Isa into theapplication zone an amount corresponding to the desired degree ofapplication of the brakes. The control pipe I! is accordingly charged toa pressure corresponding to the position of the brake valve handle, forexample fifty pounds per square inch. Being connected through the branchpipes |8 to the control pipe, brake cylinders l are charged with fluidat a pressure equal to that in the control pipe and thus effectapplication of the brakes associated with the wheels |3 to acorresponding degree.

As long as the wheel units continue to rotate at a speed correspondingto car speed without slipping, the magnet valves 3| remain deenergizedand consequently no variation of the pressure in the brake cylinders I 5occurs except that resulting from variations of the pressure in thecontrol pipe I! by operations of the brake valve l9.

If during an application of the brakes, however, any of the wheel unitsother than the underbraked wheel unit beginsto slip, the reduction inthe local frequency supplied to the phase windings A2 and B2 of thecorresponding relay 32 with respect to the master frequency supplied tothe phase windings Al and BI results in operation of the contact arm 54of the relay to establish the previously described circuit forenergizing the magnet winding of the magnet valve 3| for thecorresponding wheel truck. The magnet valve 3| is accordingly operatedto cutoff the supply of fluid under pressure to the brake cylinders ofthe truck having the slipping wheels and at the same time rapidlyexhaust fluid under pressure from the brake cylinders.

In view of the fact that operation of the contact arm 54 of the relay 32is effected whenever the local frequency supplied to the phase windingsA2 and B2 reduces a small percentage below the master frequency suppliedto the phase windings Al and B| the fluid pressure is so promptly and sorapidly reduced in the affected brake cylinders that the slipping wheelsdo not decelerate to a locked condition but begin to accelerate backtoward a speed corresponding to the car speed before reaching the lockedcondition.

As long as the rotational speed of the slipping wheel or wheel unitvaries by more than the certain low percentage from the rotational speedof the underbraked wheel unit, the contact arm 54 of the relay 32corresponding to the slipping wheel unit will remain in closed positionso that the magnet winding of the magnet valve 3| of the correspondingwheel truck remains energized. Fluid under pressure will accordinglycontinue to be vented from the brake cylinders of the truck having theslipping wheels until the slipping wheels are restored substantially toa speed corresponding to car speed.

Thus, even if a slipping wheel unit should decelerate momentarily to alocked condition, it cannot remain in a locked condition because thefluid under pressure continues to be released from the brake cylindersassociated therewith until such time as it is restored substantially tovehicle speed.

When the slipping wheel unit is restored substantially to a speedcorresponding to car speed,

the contact arm 54 of the corresponding relay 32 is restored to itsnormal position interrupting the energizing circuit for the magnetwinding 46 of the magnet valve 3| for the corresponding truck. Themagnet valve 3| is accordingly restored to its normal position closingthe exhaust communication and restoring the supply communication to thebrake cylinders. Fluid under pressure is accordingly resupplied from thecontrol pipe H to the brake cylinders of the truck having the slippingwheel unit. Such supply of fluid under pressure to the brake cylinderstends to reduce the pressure in the control pipe I! but due to thepressure-maintaining feature of the brake valve I9, fluid under pressureis automatically supplied to the control pipe H to maintain a pressuretherein corresponding to the position of the brake valve handle,notwithstanding the supply of fluid under pressure from the control pipeto the brake cylinders. Thus when a slipping wheel is restored to aspeed corresponding to car speed, the pressure restored in the brakecylinders again corresponds to that established in the control pipe II.

If upon the restoration of the pressure in the brake cylinders, thewheel unit again begins to slip, the above operation is repeated. At notime, therefore, are the Wheels permitted to reach or remain in a lockedcondition and slide.

When a vehicle comes to a stop in response to application of the brakes,the operator of the vehicle may operate the brake valve I9 to reduce thepressure in the control pipe I! so as to correspondingly reduce thepressure in the brake cylinders and the degree of application of thebrakes to prevent undesired surge at the time of stopping. After thevehicle has been brought to a complete stop, the operator may increasethe pressure in the control pipe I! and brake cylinders l5 to effect anydesired degree of application of the brakes so as to hold the vehicle onany grade encountered in service.

In order to release the brakes prior to again starting the vehicle, theoperator merely shifts the brake valve handle |9a to its brake releaseposition. The pressure in the control pipe I1 and correspondingly in thebrake cylinders I5 is reduced to atmosphere by the exhaust of fluidunder pressure through the exhaust port and pipe 28' in the brake valveand the brakes are thus completely released.

Adaptation of equipment to a train of cars In the case of a train ofcars, the equipment shown in Fig. 1 may be utilized in several ways. Forexample, in the case of modern high speed streamlined trains of thearticulated type in which a particular group of cars and a locomotiveremain coupled and do not operate ordinarily except in such trains, thetrain wires 31, 38 and 39 may be extended throughout the train, withsuitable fiexible couplers 4| connecting the sections on successivecars, and only one two-phase master frequency supply provided as on thelocomotive. In a similar manner, the bus wires 86 and 9| may be extendedthroughout all cars of the train so that only one source correspondingto the battery 88 is required on one of the cars, such as thelocomotive. Likewise the wire 62 may be extended throughout all cars ofthe train so that only one source of currentcorrespondingto the battery63 need be provided onone of the cars, such as the locomotive, forenergizing the magnet windingsof the magnet valves 3| on the severalcars.

On the other hand, if desired, each car may operate as a separate unitwith respectto the control of the relays 32 thereon. In such case, eachcar requires a master frequency supply corresponding to that associatedwith the underbraked wheel unit in Fig. 1 and no connection between thesections of wires 31, 38, 39, 62, 86 and 9| on the several cars need beeffected. In addition, each car would be provided with separate sourcesof direct-current corresponding to the batteries 63 and 88.

Modification shown in Fig. 3

Referring to Fig. 3, a modified form. of relay 32a may be providedinplace of. the relays 32 in Fig. l. The relay 32a. differs from the relay32.

phase current associated with the corresponding wheel unit. In view ofthe fact that. the rotary. movement of the rotor 52a is small, flexiblelead wires are provided to connect the secondary windings 34s and 35s ofthe local source of twophase current to the phase windings A2 and B2. Ifdesired, however, the rotor 52a may be provided with three conventionalcollector rings to which the phase windings A2 and B2 are respectivelyconnected; and the connections to the secondary windings of thetransformers 34 and 35 may be made through brushes contacting the threecollector rings in manner not shown.

The phase windings AI' and BI are arranged in the stator frame (1 in thesame manner as in the relay 32.

Th phase windings Al and Bi of relay 32a produce a rotating magneticfield which causes a torque to be exerted on the rotor 52a in adirection to operate the contact arm 54 in a counterclockwise directionso as to effect engagement of the contact 58 thereon with the associatedpair of stationary contacts 59 and 60.

The phase windings A2 and B2 on the rotor 52a are so arranged andconnected as to produce a magnetic field rotating in the oppositedirection and causing a torque to be exerted on therotor 52a in theopposite direction and maintaining the contact arm 54 in engagement withthe stop'55 as long as the respective frequencies of the two-phasecurrent supplied to the phase windings in the stator and in the rotor donot differ bymore than a certain small percentage.

When a Wheel unit slips and the frequenc of the two-phase currentsupplied to the phase windings A2 and B2 on the rotor 52a is reducedrelative to the frequency of the two-phase current supplied to thestator phase windings Al and BI, the unbalanced torque exerted on therotor 52a by the stator phase windings Al and Bi causes the contact arm54- to be shifted in a counterclockwise direction to effect theengagement of the contact 58 on the contact arm with the associated pairof contacts 59-and 60.

Summary Summarizing, it will be seen that we have provided a novelarrangement for detecting a differential in the speeds of two separatelyrotatable elements. This arrangement comprises a relay of the inductionmotor type in either of two forms. In one form, one set of two-phaseWindings is arranged in the'stator portion of the relay and energized bya two-phase supply at a frequency proportional to-thespeed of one of therotatable elements so as to produce'a magnetic field rotatable in onedirection and exerting a torqueon a squirrel-cage rotor inacorresponding direction. Another set of two-phase windings is arrangedin the stator of the relay and energized at a frequency corresponding tothe rotational speed of the other rotary element so as to produce amagnetic field rotating in the opposite direction and exerting anequivalent or slightly greater torque in the opposite direction onthe-squirrel-cage rotor.

As long as the frequency of: the two-phase alternating current suppliedrespectively to the'two sets of two-phase windings does not differ bymore than a certain percentage, the squirrelcage rotor remains in acertain normal position maintaining a contact arm thereof in circuitopcnposition. When the frequency of the twophase supply to one of the setsof windings difiers by more than a certain amount fromthe frequency ofthe two-phase supply to the other set of windings, the unbalanced torqueon the rotor rotates it a limited amount. in. a corresponding directionto effect movement of the contact arm to a circuit-closing position.

We have utilized the above-described arrangement to compare therotationalspeeds of' individual wheel unitson a vehicle with therotational speed'of' a wheel unit-which rotates atall timesincorrespondence with the speed of. the vehicle as a means fordetecting, the slipping condition of the wheels and'effecting arapidreduction: in the degree of application associated with the slippingwheels so as to cause them to be restored to a speedcorrespondi'ng tovehicle speed without" decelerating to a locked condition and sliding. Amodifiedv form of? two-phase relay of. the induction motor type fordetecting the difference in rotational speeds oftworotaryelements isprovided which differs from the first form in that the one set of phasewindings is provided in the stator of the relay and the other set ofphase windings is provided on the rotorof the relay.

While wehave illustrated our invention in connectionwith a specific formof. brake control equipment, it willbe understood that the specific ,notour intention to limit the scope of our invention except in accordancewith the terms of the appended claims.

Having now described our invention, what we claim as new and desire tosecure by Letters Patent, is:

1. In a brake control equipment for a wheeled vehicle of the type havingmeans under the control of the operator for effecting application andrelease of the brakes associated with the vehicle wheels, incombination, means for supplying a polyphase voltage at a frequencyproportional to the rotational speed of one wheel unit, means forsupplying a polyphase voltage at a frequency proportional to therotational speed of another wheel unit, and means effective upon theoccurrence of at least a certain difference in the frequencies suppliedby said polyphase supply means for causing a variation in the degree ofapplication of the brakes associated with at least one of said wheelunits.

2. In a brake control equipment for a wheeled vehicle of the type havingmeans under the control of the operator for effecting application andrelease of the brakes associated with the vehicle wheels, incombination, means for supplying a polyphase voltage at a frequencyproportional to the rotational speed of one wheel unit, means forsupplying a polyphase voltage at a frequency proportional to therotational speed of a different wheel unit, and means controlledaccording to the relation of the frequencies supplied by said twopolyphase supply means for effecting a reduction in the degree ofapplication of the brakes associated with at least one of said wheelunits upon the occurrence of a predetermined difference in thefrequencies supplied by said two polyphase supply means.

3. In a brake control equipment for a wheeled vehicle of the type havingmeans under the control of the operator for effecting application andrelease of the brakes associated with the vehicle wheels, incombination, means for supplying a master polyphase voltage at afrequency proportional to the rotational speed of one wheel unit of thevehicle, means for each of a plurality of other wheel units forsupplying a polyphase voltage at a frequency proportional to therotational speeds of the corresponding wheel units, and individual meansfor each of said other wheel units controlled according to the relationof the frequency of the master polyphase voltage and the frequency ofthe voltage of the polyphase supply means of the corresponding wheelunit for effecting a continued reduction in the degree of application ofthe brakes associated with a corresponding one of the said other wheelunits as long as a predetermined difference in the frequencies of thetwo polyphase voltages exists.

4. In a brake control equipment for a wheeled vehicle of the type havingmeans under the control of the operator for effecting application andrelease of the brakes associated with the wheels of the vehicle, incombination, means for supplying a polyphase voltage at a frequencyproportional to the rotational speed of one wheel unit, means forsupplying a polyphase voltage at a frequency proportional to therotational speed of a different wheel unit, and means controlledaccording to the relation of the frequencies supplied by said twopolyphase supply means and effective upon a reduction of the frequencyof the polyphase voltage supplied by the polyphase supply meanscorresponding to said different wheel unit when such wheel unit slipsfor effecting a reduction in the degree of application of the brakesassociated with said different wheel unit.

5. In a brake control equipment for a wheeled vehicle of the type havingmeans under the control of the operator for effecting application andrelease of the brakes associated with the vehicle wheels, incombination, means for supplying a polyphase voltage at a frequencyproportional to the rotational speed of one wheel unit; means forsupplying a polyphase voltage at a frequency proportional to therotational speed of a different wheel unit; and a relay device having astator with two sets of polyphase windings, one of which sets isenergized by current supplied from the polyphase supply meanscorresponding to said one wheel unit and adapted to produce a magneticfield rotating in one direction and the other of said sets of windingsbeing energized by current supplied from the polyphase supply meanscorresponding to the said different wheel unit and adapted to produce amagnetic field rotating in the opposite direction, and a normallystationary rotor on which the torque forces respectively resulting fromthe two rotating magnetic fields are exerted in substantially balancedrelation as long as the frequencies of the polyphase voltages suppliedto the two sets of windings do not differ by more than a certain amountand operative out of its normal position to effect a reduction in thedegree of application of the brakes associated with said different wheelunit when the said different wheel unit slips and the frequency of thepolyphase voltage corresponding thereto differs by more than saidcertain amount with respect to the frequency of the polyphase voltagecorresponding to said one wheel unit.

6. Vehicle brake control equipment of the type having means under thecontrol of the operator for effecting application and release of thebrakes associated with the vehicle wheels, comprising in combination,means for supplying a polyphase alternating current voltage having afrequency proportional to the rotational speed of one wheel unit, meansfor supplying a polyphase alternating current voltage having a frequencyproportional to the rotational speed of another wheel unit, and anelement subject to two oppositely exerted forces respectivelyproportional to the frequency of the voltage supplied by said twovoltage supply means, said element being normally stationary as long asthe respective frequencies of the voltages supplied by the two supplymeans do not differ by more than a certain percentage and operative outof its stationary position when the frequency of the voltage su-ppliedby one of said supply means differs by more than said certain percentagewith respect to the frequency of the voltage supplied by the othervoltage supply means to effect a reduction in the degree of applicationof the brakes.

'7. Vehicle brake control equipment of the type having means under thecontrol of the operator for effecting application and release of thebrakes associated with the vehicle wheels, comprising in combination,means for supplying an alternating current voltage having a frequencyproportional to the rotational speed of one wheel unit, means forsupplying an alternating current voltage having a frequency proportionalto the rotational speed of another wheel unit, a rotary element, meansfor exerting a torque on said rotary element proportional to thefrequency of the voltage supplied by one of said supply means and urgingsaid rotary means in one direction, means for exerting a torque on saidrotary element proportional to the frequency of the voltage delivered bythe other of said voltage supply means and urging the rotary element inthe opposite direction, means yieldingly resisting rotary movement ofsaid rotary means out of a certain position unless the frequency of thevoltage delivered by one of said voltage supply means diifers by morethan a certain per cent with re spect to the frequency of the voltagedelivered by the other said voltage supply means, and means responsiveto the movement of said rotary means out of its certain position foreffecting a reduction in the degree of application of the brakesassociated with at least one of said wheel units.

8. The method of controlling the brakes associated with the wheels of avehicle so as to prevent sliding of the wheels, which method comprisesproviding a polyphase alternating current voltage having a frequencyproportional to the rotational speed of one wheel of the vehicle,providing a second polyphase alternating current voltage having afrequency proportional to the rotational speed of a second wheel of thevehicle, and altering the degree of application of the brakes associatedwith at least one of the wheels upon the occurrence of a predetermineddifference in the relation of the frequencies provided.

9. The method of controlling the brakes associated with the wheels of avehicle so as to prevent the sliding thereof, which method comprisesproviding a polyphase alternating current voltage having a frequencyproportional to the rotational speed of one wheel of the vehicle,providing a second polyphase alternating current voltage having afrequency proportional to the rotaall tional speed of a differentseparately rotatable wheel of the vehicle, and effecting a reduction inthe degree of application of the brakes associated with at least one ofthe wheels whenever the two frequencies differ by more than a certainper cent.

10. Brake control apparatus for a vehicle having two separatelyrotatable wheels comprising in combination, means for supplying fluidunder pressure to effect application of the brakes associated with thesaid wheels, fluid pressure operated means responsive to a givenpressure of fluid supplied by said means for effecting application ofthe brakes on one of said wheels to one degree, fluid pressure operatedmeans responsive to the given pressure of fluid supplied for effectingapplication of the brakes on the other of said wheels to a lesserdegree, means for supplying a polyphase voltage at a frequencyproportional to the rotational speed of said one wheel, means forsupplying a polyphase voltage at a frequency proportional to therotational speed of said other wheel, and means responsive to adifference in the frequencies of the voltages supplied by said twovoltage supply means of at least a certain amount for effecting areduction in the pressure of the fluid supplied to the fluid pressureoper ated means effecting application of the brakes on the said onewheel.

11. The method of controlling the brakes associated with a plurality ofseparately rotatable vehicle wheels so as to prevent sliding of thewheels, which method comprises providing a polyphase alternating currentvoltage having a frequency proportional to the rotational speed of onewheel of the vehicle, providing a second polyphase alternating currentvoltage having a frequency proportional to the rotational speed of asecond Wheel of the vehicle, producing by said polyphase voltagescorresponding mangetic fields rotating in opposite directionsrespectively, and causing a reduction in the degree of application ofthe brakes associated with at least one of the wheels upon theoccurrence of a predetermined difference in the rotational speeds of themagnetic fields.

JOHN CANETTA. PAUL N. BOSSAR'I.

